What was found
FLT 743 - MCO-SJU, RETURN TO MCO, EXTREME CABIN V/S FLUCTUATION IN CLIMB PLUS 2000 FT TO MINUS 1500 FT. NO ECAM SWITCHED TO MAN SYS 1, SYS 2 WITH NO EFFECT. CABIN PRESSURE WENT TO 9800 FT AT 370. INITIATED DESCENT AND FLUCTUATIONS IMMEDIATELY STOPPED. SYSTEM NORMAL FOR REST OF FLIGHT. PERFORMED TSM 21-61-00. REMOVED AND REPLACED PACK 1 CONTROLLER REF AMM 21-61-34 AND PACK 2 CONTROLLER PRECAUTIONARY. PERFORMED BLEED AIR SYS TEST REF 36-11-00 AND CPC TEST REF 21-30-00. ALL CHECKS OK. OK FOR SERVICE.